Various types of display panels and display fields are known, in which one or more lamps are located behind a panel. The lamps may have reflectors in order to reflect light emitted from the lamps to the area to be illuminated. The efficiency of illumination is low, since the ratio of the light which is generated to that which actually passes through the panel is low. The uniformity of illumination, likewise, is frequently unsatisfactory unless a large number of lamps are used.